Cleaning appliances, such as dishwashers or clothes washers, use multiple treating chemistries and combinations of treating chemistries to achieve better cleaning. Before choosing a treating chemistry, a user may take into account the type and quantity of the items being cleaned along with the type and quantity of soils and stains on the items. There are many different types of treating chemistries, e.g. detergents, bleach, enzymes, anti-spotting agents, aroma agents, etc. Some of these treating chemistries are deleterious to another chemistry's efficacy. An example is bleach, which is known to destroy certain enzymes found in detergents. Therefore, it may be desirable to control the dispensing of the treating chemistries in such a way as to avoid these negative consequences.
This problem is exacerbated in bulk dispensing systems, which often use multiple refillable or replaceable containers, with each container coupled by its own supply line directly to the treatment chamber or to a common header that supplies the treatment chamber. Residual treating chemistry often remains in the supply line. If a consumer refills a container with a new chemistry that may be incompatible with the prior chemistry, the supplying of the new chemistry through the residual chemistry may reduce the efficacy of the new chemistry and negatively impact the cleaning performance of the appliance.